"Don't you think a little mystery is a good idea?" Zellweger, 47, asked ET's Deidre Behar. "I might just be lazy and think that it's too much of a commitment to post things."

"I try to call my mom during the day and answer the row of emails that have come in," she added. "That seems like enough for me, and I don't know that tweeting is always a safe bet, depending on how emotional your day is."

For Reeves, it's a "privacy" thing.

"[Privacy] is important to me," the 52-year-old actor explained. "And yeah, I don't really have anything to say about anything!"

Reeves echoed her sweet sentiments, telling ET, "Just being a fan of [Zellweger's] work and to actually see it in person and have the honor of playing together to tell a story together was just like, 'Oh my gosh, you are really, really, really good!'"